In an engine or other complicated structure, the rigid body characteristics (mass, center of mass position, three main inertia moments, orientations of three principal axes corresponding to these, etc.) are some of the biggest factors governing the motion performance or vibration/noise performance and performance in vibration/noise control of the structure. In actuality, the values of the rigid body characteristics are the most important parameters when starting a broad range of analysis, design, and optimization of dynamic behavior such as in motion analysis, vibration analysis, vibration dampening mechanism design and analysis, and control system design and analysis for assisting design. Therefore, easy identification (measurement) of the rigid body characteristics of a complicated structure by a practical precision is extremely important.
As the method of identification of such rigid body characteristics, the present inventors have proposed the method christened the “Experimental Characteristic Matrix Identification Method” (PLT 1). In this method, the measurement target is treated as an elastic body, springs etc. are used to flexibly support the measurement target, a single-point vibration, multi-point response test is run in that state, and the rigid body characteristics are found from the first order to second order or third order suitable number of resonance vibration characteristics which are obtained by the tests.